If you want to utilize TSA Pre, you must apply for it. If you apply and get granted Global Entry, it will include TSA Pre. TSA Pre is for use with domestic (i.e. USA only flights) and Global Entry is for use with international re-entry and even if you have your Global Entry tied to your passport, you may need your Global Entry card. We didn't need it for re-entry from Mexico, but a friend just returned from Canada and she needed it to utilize Global Entry.
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